I have a turntable (Project Debut III) that is producing a low hum (not
rumble - no pumping woofers) during silent sections of the record. It
is grounded, and the transport screws are removed. There is very only a
very slight (volume past halfway to hear it) hum when the needle is not
on the record, and this can be stopped by unplugging the CD player.

Can I assume that it is not an interference problem? Does anyone have
any ideas why this might happen? The motor seems to be vibrating a
little when I touch it, but not audibly, and it is suspended from the
plinth by an "elastic band" type device.

On 12 Feb 2006 09:15:20 -0800, "dodecatheon"
wrote:

I have a turntable (Project Debut III) that is producing a low hum (not
rumble - no pumping woofers) during silent sections of the record. It
is grounded, and the transport screws are removed. There is very only a
very slight (volume past halfway to hear it) hum when the needle is not
on the record, and this can be stopped by unplugging the CD player.

Can I assume that it is not an interference problem? Does anyone have
any ideas why this might happen? The motor seems to be vibrating a
little when I touch it, but not audibly, and it is suspended from the
plinth by an "elastic band" type device.

If it stops when you unplug the CD player, you have a ground loop. Is
the metalwork of th CD player making contact with the turntable?
Otherwise does it have a mains ground as well as those in the signal
leads? You need to get rid of one of these grounds somehow.

d

Pearce Consulting
http://www.pearce.uk.com

Sorry. I was a bit unclear.

1) There is a hum that occurs when the needle is on the record. This is
fairly significant.

2) There is also a very faint hum when the cd player is plugged in.
This occurs whether the needle is on the record or not. This is not
really a problem.

What could be causing hum #1?

On 12 Feb 2006 12:26:16 -0800, "dodecatheon"
wrote:

Sorry. I was a bit unclear.

1) There is a hum that occurs when the needle is on the record. This is
fairly significant.

2) There is also a very faint hum when the cd player is plugged in.
This occurs whether the needle is on the record or not. This is not
really a problem.

What could be causing hum #1?

OK - does it make a difference if the turntable is spinning? If so,
the problem could be a poorly shielded cartridge picking up the
magnetic field of the motor.

d

Pearce Consulting
http://www.pearce.uk.com

It only happens when the motor is turning, but it is only audible when
the needle is on the record.

"dodecatheon" wrote in message
ups.com...
It only happens when the motor is turning, but it is only audible when
the needle is on the record.


It might be picking up a mechanical vibration - like from the fans in a
computer case. Happened to me...

Mark Z.

"dodecatheon" wrote in message
ups.com...
It only happens when the motor is turning, but it is only audible when
the needle is on the record.


Could be bad signal wire(s) -- either inside the tonearm or turntable
body -- shorted or open as you rotate the tonearm to the record position.

I sent it back to the dealer to have a look at it. He says he can't
replicate the problem, and that it is probably a problem with my ac
power. Does this sound plausible?